Very confused on 5th wheel hitch wiring

[agraup]

Oh man am I confused. I ordered a 2008 chev silverado 2500HD diesel and had the optional "camper and 5th wheel trailer wiring provisions" put in. I'm told it's an 8 way wiring harness and an additional 7 way sealed connector routed to the front of the box.

I can't find a dealer anywhere that actually knows what that looks like or how it works. I have a 5th wheel with a 7 way plug and what I'm wondering is:

1) Can I plug the 5th wheel into the front of the box into the 7 way sealed connector that they're supplying?

2) Is the connector at the front of the box installed to the box itself?

One hitch shop I've talked to said they don't use the wires that chev puts at the front of the box but instead, they put a new plug into the side of the box at the back. He didn't explain why other than he didn't like the way it's wired at the front of the box.

If it comes with a 7 way connector at the front of the box, why put a new one in at the back?

Also, all the plugs I've seen are 7 way, what's the 8 way for?

Sorry for all the questions but I'm so confused and tired of getting the run around from dealers and hitch shops.

Hopefully someone on this site can give me some info and advice.

thanks,
AG

[75K30]

Welcme to the site;
Sounds like you are getting some bum information there. Have you opened up the plug to count how many posts there are? You should only have seven. Can't imagine what the 8th one would actually do.
In most cases a fiver connection in the box is done one of two ways.
1. use the existing plug, and add an extension cable to reach gooseneck, or 5th wheel
2. Isolate the rear plug, and add a new plug that mounts where ever you like.
These kits are pretty cheap, and with just a little troubleshooting, you should be able to figure everything out.
Here is an example.
5TH WHEEL-GOOSENECK WIRING

Here is a typical 7 way diagram, you should be able to verify your own wiring.
Trailer Wiring Diagram For 4 way, 6 way and 7 way circuits

[agraup]

thanks for the quick reply.

I wish I could open the plug but I can't because I don't have the truck yet. It's on order and should be here in 6-8 weeks. Everything I own has a 7 way plug or connector. I can't image what the 8th wire does either.

The dealer told me that the 8 way is new so people don't need an adapter. This doesn't make any sense to me.

Have you ever seen the factory option for the 5th wheel trailer mounted to the front of the box? It seems like there is a 7 way at the front of the box as well. Just wondering if anyone has actually seen this setup.

I guess things will be clearer when I actually get the truck and see what things look like.

thanks for your input.

AG

[75K30]

Well good luck with your plug. I am pretty confident that the individual providing you with the information is simply mistaken and told you 8 posts instead of 7. I mean all we realy need is 6. The seventh is either an aux 12VDC, or back up lights (which is what I use them for) and an 8th is a little bit of a puzzle, but who knows?
Again good luck, and perhaps the lcation is not much of an issue. This remote location might keep a tidy bed, and keep the plug out of sight. May require an extension to actually reach the trailer, but I guess this is all speculation until the truck arrives.
Ohhh the wait. lol.

[agraup]

I finally got the scoop on this issue from a reputable hitch installer. It took about 5 different companies to find one that knew what he was talking about. (Dan from Car Guys in Calgary)

A group of wires for both a 7 way and an 8 way are grouped together and attached to the front of the box between the cab and the box. This is what they are reffering to at the dealer as the "provisions for a fifth wheel and trailer" that comes with the Z82 trailering suspension.

When you get the 5th wheel hitch installed they can take those wires and run them to anywhere in the box where you want a plug installed. If you want to utilize a tool box at the front of the box (depending on the size of the tool box), you get the plug mounted at the rear of the box. Anyway, there is no plug attached to these wires or mounted anywhere in the box from the factory. When you install the 5th wheel hitch, a hole is cut somewhere in the box if you want to flush mount the plug.

I was told that when you get the wires at the front of the box hooked up to a plug, you must connect two of the wires under the hood. One for your RV batteries and the other for the electric brakes. Chev doesn't hook up all the wires under the hood; that's left for the person that puts a plug onto these wires.

A person could just hang the 5th wheel plug over the tail gate and utilize the existing plug on the bumper.

Now I wait for delivery of the truck.

[75K30]

Valuable information, thanks for the update.

[crabtruck]

Welcome to the forum AG. Would love to see a wiring diagram of the 8 way wires when the truck shows up. How long a wait are you facing ?

[75K30]

Crab:
any ideas on the 8 way? New to me, and I cant figure out what the 8th lead could be used for.
What am I missing?

[crabtruck]

Being an old Norris fan, I was thinking Octagon.
Really I got nothing so far, probably a redundant circuit.
Or folks are getting crazy with back-up cameras, sig-over-voltage ?
Got me curious though... I'm gonna see what I can find out.

[crabtruck]

This is what I have found so far, but not conclusive.
The 2006 I was looking at had the 7 wire harness:
WHT.. ..(B) GROUND
YEL......(G) LT TRLR ST/TURN 10A FUSE
DkGrn...(D) RT TRLR ST/TURN 10A FUSE
LtGrn....(A) BACK-UP LAMPS
RED......(E) 40A HOT AT ALL TIMES
DkBlu....(C) BRAKE CONTROL
BRN......(F) TRL PARK 10A FUSE
Odd colors too.

Whereas the 96 I was looking at had 8 wire harness:
BLK.......... PLATFORM HITCH GROUND
WHT........ GROUND
YEL......... LT ST/TURN HAZ SWITCH
DkGrn...... RT ST/TURN HAZ SWITCH
LtGrn....... BACK-UP LAMPS
RED......... HOT AT ALL TIMES
DkBlu....... AUX/BRAKE CONTROL
BRN......... TAIL/PARK